Several naturally-occurring alkaloids obtainable from Vinca rosea have been found active in the treatment of experimental malignancies in animals. Among these are leurosine (U.S. Pat. No. 3,370,057), vincaleukoblastine (vinblastine or VLB) (U.S. Pat. No. 3,097,137), leurosidine (vinrosidine) and leurocristine (VCR or vincristine) (both in U.S. Pat. No. 3,205,220). Two of these alkaloids, VLB and leurocristine, are now marketed as drugs for the treatment of malignancies, particularly the leukemias and related diseases, in humans. Of these marketed compounds, leurocristine is a most active and useful agent in the treatment of leukemias, but is also the least abundant of the anti-neoplastic alkaloids of Vinca rosea.
Other dimeric indole alkaloids which have been isolated from Vinca rosea but which are less active antimitotically than VLB and leurocristine include leurocolombine (2'-hydroxy VLB), vincadioline (3'-hydroxy VLB), 4-desacetoxy VLB (psuedo VLB), leuroformine and isoleurosine (deoxy VLB "B"). Vincadioline is disclosed in copending U.S. application Ser. No. 466,939 filed May 6, 1974, leuroformine is disclosed in copending U.S. application Ser. No. 469,981 filed May 15, 1974, and leurocolombine is disclosed in U.S. application Ser. No. 469,982 filed May 15, 1974.